1. Technical Field of the Invention
The present invention relates to integrated circuits and more particularly to integrated circuits comprising photosensitive elements temporarily exposed to visible radiation.
2. Description of Related Art
Integrated photosensitive elements are widely used at the present time in photographic equipment—such as, digital cameras or detectors. In theory, and contrary to silver films, the integrated photosensitive elements may detect, almost continuously, visible radiation without being irreversibly modified by said radiation. It is therefore possible to expose integrated photosensitive elements during set-up phases or during any other period when the detected image is not being recorded. During these periods, the detected image can be displayed, for example using a screen, and the recording takes place at the moment desired by the user, when the detected image corresponds to that desired. One of the consequences of the operation of these photosensitive elements is the absence of a shutter—the image is recorded electronically and no longer mechanically. The integrated photosensitive elements are therefore continuously exposed and must remain operational throughout the lifetime of the equipment.
Now, it is apparent that the integrated photosensitive elements such as photodiodes may become degraded due to the effect of the light. This is because photons reaching a photodiode normally create electron-hole pairs generating an electrical current proportional to the number of photons received by the photodiode. Now, it turns out that an electron-hole pair recombines within the photodiode, releasing energy liable to damage the molecular bonds of the material forming the photodiode. As a result, the photosensitive element may lose its sensitivity or its effectiveness because of prolonged exposure to the radiation. It is therefore necessary to reduce the exposure of these elements.
Hitherto, systems used for controlling the opening and closing of photographic equipment act as shutters, which open temporarily or close. Such systems cannot be envisaged for equipment fitted with photodiodes, as they would prevent the image from being detected outside the recording periods. It would therefore no longer be possible to make adjustments while displaying the detected image on a screen. It is consequently necessary to provide equipment that takes advantage of photodiodes while limiting the ageing due to prolonged exposure of said photodiodes to light.
There is a need to remedy the abovementioned drawbacks. The present invention proposes an integrated circuit capable of continuously detecting an image while limiting the deterioration of the integrated circuit.